1. Field of the Invention
The present invention relates in general to a brake pedal apparatus, and more particularly to such a brake pedal apparatus having a high degree of freedom in setting of a lever ratio characteristic.
2. Discussion of Prior Art
There is known a brake pedal apparatus having (a) an operating pedal which is disposed pivotably about a first axis, (b) a pivot member which is disposed pivotably about a second axis parallel to the first axis, and which is connected to the operating pedal via a connecting link so as to be mechanically pivoted about the second axis in response to a depressing operation effected on the operating pedal; and (c) an output member which is to be mechanically pressed or pulled as a result of pivot motion of the pivot member. As an example of such a brake pedal apparatus, Patent Document 1 discloses an apparatus in which a lever ratio representative of a ratio of an output to a depression force acting on the operating pedal is changed in accordance with a pedal stroke. Further, Patent Document 2 discloses a technique for transmitting a depression force from an operating pedal to a pivot member by employing a cam and a roller in place of the above-described connecting link.
Patent Document 1: JP-H7-205776A
Patent Document 2: JP-H5-185912A
However, in such a conventional brake pedal apparatus, since a characteristic of change of the lever ratio (lever ratio characteristic) is dependent on connected positions of the connecting link and contour of the cam, it is difficult to largely change the lever ratio halfway during the pedal stroke. Thus, the change in the lever ratio is not necessarily satisfactory.
The present invention was made in the light of the background art discussed above. It is therefore an object of the invention to provide a bake pedal apparatus which is capable of easily changing the lever ratio by a large amount halfway during the pedal stroke and which has a high degree of freedom in setting of a lever ratio characteristic.